Covalent Graphene‐MOF Hybrids for High‐Performance Asymmetric Supercapacitors
Kolleboyina Jayaramulu, Michael Horn, Andreas Schneemann, Haneesh Saini, Aristides Bakandritsos, Václav Ranc, Martin Petr, Vitalie Stavila, Chandrabhas Narayana, Błażej Scheibe, Štěpán Kment, Michal Otyepka, Nunzio Motta, Deepak P. Dubal, Radek Zbořil, Roland A. Fischer
Abstract
Abstract In this work, the covalent attachment of an amine functionalized metal‐organic framework (UiO‐66‐NH 2 = Zr 6 O 4 (OH) 4 (bdc‐NH 2 ) 6 ; bdc‐NH 2 = 2‐amino‐1,4‐benzenedicarboxylate) (UiO‐Universitetet i Oslo) to the basal‐plane of carboxylate functionalized graphene (graphene acid = GA) via amide bonds is reported. The resultant GA@UiO‐66‐NH 2 hybrid displayed a large specific surface area, hierarchical pores and an interconnected conductive network. The electrochemical characterizations demonstrated that the hybrid GA@UiO‐66‐NH 2 acts as an effective charge storing material with a capacitance of up to 651 F g −1 , significantly higher than traditional graphene‐based materials. The results suggest that the amide linkage plays a key role in the formation of a π‐conjugated structure, which facilitates charge transfer and consequently offers good capacitance and cycling stability. Furthermore, to realize the practical feasibility, an asymmetric supercapacitor using a GA@UiO‐66‐NH 2 positive electrode with Ti 3 C 2 T X MXene as the opposing electrode has been constructed. The cell is able to deliver a power density of up to 16 kW kg −1 and an energy density of up to 73 Wh kg −1 , which are comparable to several commercial devices such as Pb‐acid and Ni/MH batteries. Under an intermediate level of loading, the device retained 88% of its initial capacitance after 10 000 cycles.